Lamp device for vehicle

ABSTRACT

A shape of a vertical cross section and a shape of a horizontal cross section in a lens are formed in a convex shape. Accordingly, even when a prism is not formed, alight transmitting through the lens is largely refracted and an interior section is hard to be visible. As a result, it is not necessary to finish a surface of a reflection surface of a reflector so as to have an optical performance equal to or more than an optical performance required for reflection with taking an appearance into consideration, and a working operation can be easily executed in comparison with the conventional one.

FIELD OF THE INVENTION

[0001] The present invention relates to a lamp device for a vehicle, forexample, a head lamp for a motor vehicle, a fog lamp for a motor vehicleor the like which lights a forward section of the motor vehicle. Inparticular, the invention relates to a lamp device for a vehicle inwhich a light distributing function is mainly given to a reflector side.

BACKGROUND OF THE INVENTION

[0002] In a recent lamp device for a vehicle, a reflection surface of areflector is formed in a free curves surface and a light distributingfunction is given to a side of the reflector. Further, in the recentlamp device for the vehicle, a so-called plain lens is used as a lensthereof and a function of an outer cover is given to a side of the lens.The plain lens corresponds to a lens in which a prism for lightdistribution is not formed and the light transmits as it is withoutbeing refracted. That is, the plain lens is constituted by a lighttransmitting member formed in a plate (a flat plate, a curved plate)shape such as a simple plate glass or the like.

[0003] However, in the conventional lamp device for the vehicle, thereflection surface of the internal reflector is clearly visible throughthe plain lens from an external section. Accordingly, it is necessarythat the conventional lamp device for the vehicle is finished so as tohave at least an optical performance required for reflection on asurface of the reflection surface of the reflector, and this workingoperation is troublesome.

[0004] Accordingly, the inventors of this invention have invented a lampdevice for a vehicle in which an interior section is made hard to bevisible in comparison with the plain lens (Japanese Patent ApplicationNo. 11-209331 (Japanese Patent Application Laid-Open No. 2001-35215).

SUMMARY OF THE INVENTION

[0005] It is an object of this invention to provide a lamp device for avehicle in which a surface finishing process of a reflection surface ina reflector can be easily executed than the conventional one by makingan interior section hard to be viewed in comparison with a plain lens.

[0006] In order to achieve the object, according to one aspect of thepresent invention, there is provided the lamp device for a vehiclewherein, a shape of a vertical cross section and a shape of a horizontalcross section in a lens are convex shapes.

[0007] As a result, in accordance with the invention, since the shape ofthe vertical cross section and the shape of the horizontal cross sectionin the lens have the convex shape, a light transmitting through the lensis largely reflected without a prism being formed, whereby the interiorsection becomes hard to be viewed. Accordingly, in accordance with theinvention, it is not necessary to finish the surface of the reflectionsurface of the reflector so as to have an optical performance equal toor more than an optical performance required for reflection with takingan appearance into consideration, and the working operation can beeasily executed in comparison with the conventional structure.

[0008] Other objects and features of this invention will becomeunderstood from the following description with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a vertical cross sectional view which shows a summary ofa head lamp for a motor vehicle in accordance with an embodiment of theinvention;

[0010]FIG. 2 is a horizontal cross sectional view;

[0011]FIG. 3 is a front elevational view;

[0012]FIG. 4 is a perspective view of a lens;

[0013]FIG. 5 is a front elevational view of a reflection surface;

[0014]FIG. 6 is a flowchart showing a method of manufacturing thereflection surface;

[0015]FIG. 7A is a front elevational view for explanation showing a datainput to an optical simulation;

[0016]FIG. 7B is a cross sectional view along a line B-B in FIG. 7A;

[0017]FIG. 7C is a cross sectional view along a line C-C in FIG. 7A;

[0018]FIG. 7D is an enlarged view of a section D in FIG. 7C;

[0019]FIG. 8A is a explanatory view which shows a representative lightdistribution pattern given by a pin point P₁ in FIG. 5 projected on ascreen;

[0020]FIG. 8B is an explanatory view which shows a representative lightdistribution pattern given by a pin point P₂ in FIG. 5 projected on thescreen;

[0021]FIG. 9 is an equiluminous curve showing a target distributionpattern of a low beam given by the head lamp for the motor vehicle inaccordance with the first embodiment;

[0022]FIG. 10 is an explanatory view of a light distribution patternbriefly showing a light distribution pattern obtained by a lens shown inFIGS. 1 to 4 and a first reflection surface block 21 from the left ofthe reflection surface 4 shown in FIG. 5, which is obtained inaccordance with a simulation of a computer;

[0023]FIG. 11 is an explanatory view of a light distribution patternbriefly showing a light distribution pattern obtained by the lens 1shown in FIGS. 1 to 4 and a second reflection surface block 22 from theleft of the reflection surface 4 shown in FIG. 5, which is obtained inaccordance with the simulation of the computer;

[0024]FIG. 12 is an explanatory view of a light distribution patternbriefly showing a light distribution pattern obtained by the lens 1shown in FIGS. 1 to 4 and a third reflection surface block 23 from theleft of the reflection surface 4 shown in FIG. 5, which is obtained inaccordance with the simulation of the computer;

[0025]FIG. 13 is an explanatory view of a light distribution patternbriefly showing a light distribution pattern obtained by the lens 1shown in FIGS. 1 to 4 and a fourth reflection surface block 24 from theleft of the reflection surface 4 shown in FIG. 5, which is obtained inaccordance with the simulation of the computer;

[0026]FIG. 14 is an explanatory view of a light distribution patternbriefly showing a light distribution pattern obtained by the lens 1shown in FIGS. 1 to 4 and a fifth reflection surface block 25 from theleft of the reflection surface 4 shown in FIG. 5, which is obtained inaccordance with the simulation of the computer;

[0027]FIG. 15 is an explanatory view of a light distribution patternbriefly showing a light distribution pattern obtained by the lens 1shown in FIGS. 1 to 4 and a sixth reflection surface block 26 from theleft of the reflection surface 4 shown in FIG. 5, which is obtained inaccordance with the simulation of the computer; and

[0028]FIGS. 16A, 16B and 16C are cross sectional views which show amodified embodiment of a convex shape corresponding to a cross sectionalshape of the lens.

DETAILED DESCRIPTIONS

[0029] A description will be given below of an example of an embodimentof a lamp device for a vehicle in accordance with the invention withreference to the accompanying drawings. In this case, the invention isnot limited by the embodiment.

[0030] The embodiment explains a head lamp for a motor vehicle which canobtain a light distribution pattern of a low beam (a light distributionpattern for crossing). In this case, the invention can be applied to theother lamp device for a vehicle. For example, the invention can beapplied to a head lamp for a motor vehicle which can obtain a lightdistribution pattern of a high beam, a light distribution pattern for ahigh speed travel, alight distribution pattern for an urban area traveland the like, a fog lamp for a motor vehicle which can obtain a lightdistribution pattern for a dense fog, or the like.

[0031] The head lamp for the motor vehicle in accordance with theinvention is equipped in a motor vehicle sectioned in a left-handtraffic. Accordingly, in the case of a head lamp for a motor vehicleequipped in a motor vehicle sectioned in a right-hand traffic, right andleft sections are reversed on the drawing.

[0032] The head lamp for the motor vehicle in accordance with theembodiment is provided with a lens 1 arranged in a front surface of alamp housing (not shown), a light source 2 and a reflector 3. In thiscase, reference symbol S denotes an optical axis.

[0033] The lens 1 is structured, as shown in FIGS. 1 to 4, such that anouter shape seen from a front surface is formed in a circular shape (maybe formed in a rectangular shape), and a shape of a vertical crosssection and a shape of a horizontal cross section are formed in a convexshape. A prism for light distribution is not formed in the lens 1. Anon-uniform rational B-spline surface (NURBS) corresponding to a freecurved surface for light distribution is formed on a front surface and aback surface of the lens 1. The lens 1 may be made of a glass or aresin.

[0034] The light source 2 employs, for example, a halogen lamp of asingle filament or a double filament, an incandescent lamp, an electricdischarge lamp or the like (so-called H1, H3, H4, H7, H11 or the like).

[0035] A reflection surface 4 of the NURBS corresponding to the freecurved surface for light distribution is formed on an inner surface ofthe reflector 3. The reflection surface 4 takes on a high intensityfeeling of a metal on the basis of an aluminum vapor deposition, asilver color painting or the like. The reflector 3 may be integrallyformed with the lamp housing or independently formed therefrom. Further,outer shapes of the reflector 3 and the reflection surface 4 seen fromfront surfaces thereof may be formed in a circular shape or arectangular shape. Further, details of the reflection surface 4 of theNURBS are described, for example, in “Mathematical Elements for ComputerGraphics” (Devid F. Rogers, J Alan Adams).

[0036] That is, the reflection surface 4 of the NURBS in the case inwhich the front surface and the back surface use the lens 1 of the NURBScan be calculated in accordance with a general equation in the followingequation (1). $\begin{matrix}{{P\left( {u,v} \right)} = {\sum\limits_{j = 0}^{m}{\sum\limits_{k = 0}^{n}{P_{j,k}{N_{j,s}(u)}{M_{k,t}(v)}}}}} & (1)\end{matrix}$

[0037] The reflection surface 4 of the NURBS calculated in accordancewith the above equation (1) is structured such that the vertical crosssection and the horizontal cross section are formed in a substantiallyhyperboloidal surface (a surface similar to a hyperboloidal surface)smaller than the lens 1 as shown in FIGS. 1 and 2.

[0038] A parametric function of the general equation in the aboveequation (1) is shown in the following equation (2). A particularreflection surface 4 of the reflector 3 in the case of using the lens 1can be obtained by substituting a particular numeric value, for example,a point on the hyperboloidal surface or the like for the parametricfunction in the following equation (2).${N_{j,s}(u)} = \left\{ \begin{matrix}1 & \left( {{i\quad f\quad u_{j}} \leq u < u_{j + 1}} \right) \\0 & \left( {t\quad h\quad e\quad o\quad t\quad h\quad e\quad r\quad c\quad a\quad s\quad e\quad s} \right)\end{matrix} \right.$

${N_{j,s}(u)} = {{\frac{u - u_{j}}{u_{j + s - 1} - u_{j}}{N_{j,{s - 1}}(u)}} + {\frac{u_{j + s} - u}{u_{j + s} - u_{j + 1}}{N_{{j + 1},{s - 1}}(u)}}}$

${M_{k,t}(v)} = \left\{ \begin{matrix}1 & \left( {{i\quad f\quad v_{k}} \leq v < v_{k + 1}} \right) \\0 & \left( {t\quad h\quad e\quad o\quad t\quad h\quad e\quad r\quad c\quad a\quad s\quad e\quad s} \right)\end{matrix} \right.$

$\begin{matrix}{{M_{k,t}(v)} = {{\frac{v - v_{k}}{v_{k + t - 1} - v_{k}}{M_{k,{t - 1}}(v)}} + {\frac{v_{k + t} - v}{v_{k + t} - v_{k + 1}}{M_{{k + 1},{t - 1}}(v)}}}} & (2)\end{matrix}$

[0039] An example of the particular reflection surface 4 obtained in themanner will be shown in FIG. 5. The reflection surface 4 in this oneexample is vertically separated into six pieces. Boundary lines (jointlines) of these six separated reflection surface blocks (or reflectionsurface segments) 21, 22, 23, 24, 25 and 26 (21 to 26) include a type inwhich the reflection surface blocks 21 to 26 are independently visibleas shown, and a type in which the reflection surface blocks 21 to 26 arenot continuously visible.

[0040] In this case, the reflection surface 4 shown in FIG. 5corresponds to one example in which the reflection surface blocks areseparated in a vertical direction. Therefore, in accordance with theinvention, the reflection blocks may be separated in a horizontaldirection, separated in a radial direction or separated in the verticaldirection, the horizontal direction and the radial direction in asuitably combined manner. That is, the reflection surface blocks may beseparated with taking a design thereof into consideration.

[0041] In this case, since the reflection surface 4 is structured suchthat the reflection surfaces of the NURBS are combined in a compositemanner, a single optical axis in the strict sense is not provided in theoptical axis S of the reflection surface 4, however, a difference amonga plurality of optical axes is slight, and substantially the sameoptical axis is commonly used. Accordingly, in this specification andthe drawings, the substantially same optical axis is called as anartificial optical axis (or simply an optical axis) S. In the samemanner, in a focus F of the reflection surface 4 (refer to FIG. 7C), asingle optical axis in the strict sense is not provided, however, adifference among a plurality of optical axes is slight, andsubstantially the same optical axis is commonly used. Accordingly, inthis specification and the drawings, the substantially same optical axisis called as an artificial optical axis (or simply an optical axis).

[0042] A description will be given below of an example of a method ofmanufacturing the reflection surface 4 with reference to FIG. 6.

[0043] At first, in a step 1 (S1), a data is input to a microcomputer(not shown). The data is selected among a design specification and thelike in a data base with taking a design of a head lamp for a motorvehicle and a design of the motor vehicle mounting the head lamp for themotor vehicle thereon. The data includes a kind of the light source 2, asize of the reflector 3, a front surface shape of the reflection surface4, a separation of the reflection surface blocks 21 to 26, a size, afront surface shape and a back surface shape of the lens 1, a targetlight distribution pattern and the like.

[0044] In a step 2 (S2), there is executed a process of temporarilysetting the reflection surface of the reflector in accordance with acombination with a planar lens on the basis of the data input in thestep 1 so that the target light distribution pattern can be obtained.The reflection surface of the temporarily set reflector is automaticallyset on the basis of a control point on the free curved surface of theNURBS, a normal vector and the like.

[0045] In a step 3 (S3), there is executed a process of changing theplanar lens to the lens 1 in which the vertical cross section and thehorizontal cross section are formed in the convex shape, withoutchanging the reflection surface of the temporarily set reflectorobtained in accordance with the process in the step 2. At this time, inaccordance with a ray tracing method, a light distribution pattern (notshown) of an image which is formed by a process in which the lightoutput from the modeled light source 2 is reflected on the reflectionsurface of the reflector, and the reflected light is refracted by thelens and thereafter reaches on a forward screen (not shown) as anoutgoing light, can be obtained by a calculation.

[0046] In a step 4 (S4), there is executed a process of calculating adifference between the target light distribution pattern obtained inaccordance with the process in the step 2 and the light distributionpattern obtained in accordance with the process in the step 3. Thisdifference is generated by a refraction of the light in the lens 1.

[0047] In a step 5 (S5) and a step 6 (S6), there is executed a processof formally setting the reflection surface of the temporarily setreflector to the reflection surface 4 of the reflector 3 for the lens 1so that the difference calculated in accordance with the process in thestep 4 becomes 0. That is, an optimum free curved surface of the NURBSis formed by automatically correcting and deforming the free curvedsurface of the NURBS on the reflection surface so that the lightdistribution pattern obtained in accordance with the process in the step3 becomes the target light distribution pattern obtained in accordancewith the process in the step 2. The processes in the step 5 and the step6 corresponds to a process of repeating a ray tracing calculation inwhich the light output from the light source 2 is reflected on thereflection surface 4 of the reflector 3, and the reflected light isrefracted by the lens 1 and thereafter reaches on the forward screen(not shown) as the outgoing light beam, in accordance with the raytracing method.

[0048] When the difference becomes substantially 0, it is assumed thatthe reflection surface 4 of the reflector 3 for the lens 1 is formerlyset, and in a step 7 (S7), the reflection surface 4 of the formerly setreflector 3 is output.

[0049] As mentioned above, in this manufacturing method, it is possibleto manufacture the reflection surface 4 of the NURBS in the case ofusing the lens 1 in which the front surface and the back surface are theNURBS. Further, by executing the processes in the steps 2 to 6, that is,the temporarily setting step of the reflection surface of the reflector3, the difference calculating step, and the formerly setting step of thereflection surface 4 of the reflector 3 in accordance with apredetermined program by a computer, it is possible to manufacture thereflection surface 4 at a high accuracy, a high speed and a high degreeof freedom.

[0050] A description will be given in detail of a result obtained byexecuting a trial an optical design simulation of the head lamp for themotor vehicle in accordance with this embodiment. FIGS. 7A to 7D areexplanatory views which show a data input to the optical designsimulation. Data sizes in FIGS. 7A to 7D are respectively as follows.

[0051] Ar=100 mm (horizontal size of the reflector 3)

[0052] Br=100 mm (vertical size of the reflector 3)

[0053] Al=160 mm (horizontal size of the lens 1)

[0054] Bl=160 mm (vertical size of the lens 1)

[0055] T=28 mm (thickness size of the lens 1 (in the optical axis S))

[0056] Sv=0 degree (angle of incline of side surface in the lens 1 (inthe optical axis S))

[0057] Sh=0 degree (angle of incline of plane surface in the lens 1 (inthe optical axis S))

[0058] Rvo=−300 mm (radius of curvature in the side surface optical axisS of front surface in the lens 1)

[0059] Rho=−300 mm (radius of curvature in the plane surface opticalaxis S of front surface in the lens 1)

[0060] Rvi=200 mm (radius of curvature in the side surface optical axisS of back surface in the lens 1)

[0061] Rhi=200 mm (radius of curvature in the plane surface optical axisS of back surface in the lens 1)

[0062] F=22 mm (focal distance)

[0063] Lf=4.6 mm (length of filament of the light source 2)

[0064] Rf=0.73 mm (radius of filament of the light source 2)

[0065] The data is input to values in Table 1 described below. In thiscase, a condition is made so that an European Light DistributionRegulation ECE Reg. is satisfied. TABLE 1 Reflector 3 Focal HorizontalVertical distance Ar (mm) Br (mm) F (mm) 100 100 20

[0066] When lighting the light source 2 of the head lamp for the motorvehicle in accordance with the embodiment, the following result in Table2 will be obtained. TABLE 2 European Light Distribution RegulationSatisfaction Maximum light intensity 24800 (cd) Use light intensity (lm)408 Light Vertical 160 generating Horizontal 160 section Thickness 28(mm)

[0067] In the head lamp for the motor vehicle in accordance with thisembodiment, the light source 2 is turned on. Then, as shown in FIGS. 1and 2, a light L₁ output from the light source 2 is reflected on thereflection surface 4 of the reflector 3, and the reflected lights L₂ andL₃ are irradiated outward as outgoing lights L₄ and L₅ via the lens 1 onthe basis of a target light distribution pattern shown in FIG. 9. Thetarget light distribution pattern corresponds to a light distributionpattern proper to a light distribution regulation such as European LightDistribution Regulation ECE Reg. or a regulation based thereon (forexample, Japan Domestic Model Certified Regulation), North America LightDistribution Regulation, FMVSS or the like.

[0068] The target light distribution pattern shown in FIG. 9 correspondsto a light distribution pattern of a low beam sectioned in a left-handtraffic, and is controlled by the respective reflection surface blocks21 to 26 of the reflection surface 4 in the reflector 3. That is, in thereflection surface 4 of the reflector 3 shown in FIG. 5, a lightdistribution pattern shown in FIG. 10 is controlled and obtained in afirst reflection surface block 21 from the left, a light distributionpattern shown in FIG. 11 is controlled and obtained in a secondreflection surface block 22 from the left, a light distribution patternshown in FIG. 12 is controlled and obtained in a third reflectionsurface block 23 from the left, a light distribution pattern shown inFIG. 13 is controlled and obtained in a fourth reflection surface block24 from the left, a light distribution pattern shown in FIG. 14 iscontrolled and obtained in a fifth reflection surface block 25 from theleft, and a light distribution pattern shown in FIG. 15 is controlledand obtained in a sixth reflection surface block 26 from the left,respectively. By combining the light distribution pattern (FIGS. 10 to15) controlled and obtained by the respective reflection surface blocks21 to 26, the target light distribution pattern shown in FIG. 9 isobtained.

[0069] As is apparent from FIGS. 10 to 15, in the first, second andsixth reflection blocks 21, 22 and 26 from the left, since they areapart from the light source 2, the reflected light is weak. Accordingly,in these reflection blocks 21, 22 and 26, a hot zone is formed bycollecting the weak reflected lights. Therefore, the reflection surfacesof the reflection blocks 21, 22 and 26 are mainly formed in a recessedsurface shape.

[0070] On the contrary, in the third to fifth reflection blocks 23 to 25from the left, since they are close to the light source 2, the reflectedlight is strong, so that the strong reflected light simply forming aspot light is diffused. Accordingly, the reflection surfaces of thereflection blocks 23 to 25 are mainly formed in a convex surface shape.

[0071] In this case, in a design of a theoretical reflection surface 4,the light source 2 is prepared as a point light source, however, sincethe actual light source 2 has the length and the width (the radius) ofthe filament as is apparent from FIGS. 1 and 2, it is not the pointlight source but a surface light source.

[0072] Accordingly, for example, as shown in FIG. 5, when the light ofthe light source 2 is reflected at one point P₁ on the reflectionsurface 4 in the third reflection surface block 23 from the left whichis closest to the light source 2, the outgoing light L₅ output from arear end b of the light source (filament) 2 is emitted to a lower sideat an angle θ1 with respect to a horizontal line S₁, as shown in FIG. 1.On the contrary, the outgoing light L₄ output from a front end a of thelight source (filament) 2 is emitted to a lower side at an angle θ2 withrespect to the horizontal line S₁. The emitted lights L₄ and L₅ areformed in a longitudinal shape in a vertical direction substantially ina center section on the screen, as shown in FIGS. 8A and 12. Further,they are slightly inclined from the light source 2 at a difference inthe lateral direction. The angles θ1 and θ2 of the outgoing lights L₄and L₅ emitted from the lens 1 with respect to the horizontal ling S1are the same as the angle θ1 and θ2 on the screen from a horizontal lineH-H, as shown in FIG. 8A.

[0073] For example, as shown in FIG. 5, when the light of the lightsource 2 is reflected at one point P₂ on the reflection surface 4 in thesixth reflection surface block 26 from the left, the outgoing light L₅output from the rear end b of the light source (filament) 2 is emittedto an inner side at an angle θ3 with respect to a vertical line S₂, asshown in FIG. 2. On the contrary, the outgoing light L₄ output from thefront end a of the light source (filament) 2 is emitted to an inner sideat an angle θ4 with respect to the vertical line S₂. The emitted lightsL₄ and L₅ are formed in a longitudinal shape in a lateral direction in aleft side of the substantially center section on the screen, as shown inFIGS. 8B and 10. The angles θ3 and θ4 of the outgoing lights L₄ and L₅emitted from the lens 1 with respect to the vertical ling S₂ are thesame as the angle θ3 and θ4 on the screen from a vertical line V-V, asshown in FIG. 8B.

[0074] As mentioned above, the free curved surface formed on thereflection surface 4 is formed by simulating the light distributionpattern generated by the free curved surface by the computer so as toanalyze a light distribution property, thereby obtaining an optimumlight distribution pattern. Accordingly, the light distribution patternof the outgoing lights L₄ and L₅ at a time when the reflected light L₂and L₃ generated by the reflection surface 4 pass through the lens 1 soas to be irradiated outward is optimum. Further, in this embodiment,since the free curved surface (NURBS) is formed on the front surface andthe back surface of the lens 1, the light distribution function can begiven not only to the reflection surface 4 but also the lens 1, wherebya more ideal light distribution pattern can be obtained.

[0075] In particular, since the headlamp for the motor vehicle inaccordance with this embodiment is structured such that the verticalcross section and the horizontal cross section of the lens 1 are formedin the convex shape, the light is largely refracted by the lens 1 andthe interior section is hard to be visible in the case of being seenfrom the exterior section, even when the prism is not formed.Accordingly, in the head lamp for the motor vehicle in accordance withthis embodiment, it is not necessary to finish the surface of thereflection surface 4 of the reflector 3 so as to have the opticalperformance equal to or more than the optical performance required forreflection with taking the appearance into consideration, and theworking operation can be easily executed in comparison with theconventional one.

[0076] The lens 1 in accordance with this embodiment is structured suchthat the shape of the vertical cross section and the shape of thehorizontal cross section are formed in the convex shape. Accordingly, inthe vertical and horizontal sections of the lens 1, as shown in FIGS. 1and 2, the lights L₂ and L₃ diffused by the substantially hyperboloidalsurface of the reflection surface 4 are focused in the directionsubstantially extending along the optical axis S, and are irradiated tothe external section on the basis of the target light distributionpattern. As a result, in the embodiment, it is possible to construct thehead lamp for the motor vehicle in which the light generation area islarge and the reflector 3 is small. Accordingly, the embodiment ispreferably employed in the case of a vehicle body design in which alarge placing space can not be sufficiently secured in an inner sectionof a front section to which the headlamp for the motor vehicle should bemounted, particularly in the case of a compact car.

[0077] The reflection surface 4 in accordance with this embodiment isstructured such that the vertical cross-section and the horizontal crosssection are formed in the substantially hyperboloidal surface smallerthan the lens 1. Accordingly, in the vertical cross section and thehorizontal cross section of the reflection surface 4, as shown in FIGS.1 and 2, the lights L₂ and L₃ can be introduced into the lens 1 in astate of being diffused vertically and horizontally with respect to theoptical axis S. As a result, in this embodiment, the vertical crosssection and the horizontal cross section are optimum for the combinationwith the lens 1 formed in the convex shape, and as shown in FIG. 3, itis possible to easily obtain the head lamp for the motor vehicle inwhich the placing space of the inner section of the front surface (thelens 1 surface) can not be sufficiently secured.

[0078] In this case, in this embodiment, the convex shape of thevertical cross section and the horizontal cross section of the lens 1means a shape having an optical function which refracts the incidentlight in a direction moving apart (diffusing) from the optical axis S,on the vertical cross surface of the lens 1. Accordingly, the convexshape includes a shape in which only one surface is formed in a convexshape as shown in FIG. 16A, a shape in which one surface is formed in arecess surface and another surface is formed in a convex surface in moredegree as shown in FIG. 16B, a shape in which the lens is arranged in aninclined manner with respect to the optical axis S as shown in FIG. 16C,and the like.

[0079] In this embodiment, the NURBS corresponding to the free curvedsurface for light distribution is formed on the front surface and theback surface of the lens 1. However, in this invention, a free curvedsurface or a torus curved surface for light distribution other than theNURBS may be formed on the front surface and the back surface of thelens 1.

[0080] In this invention, the NURBS, the free curved surface or thetorus curved surface corresponding to the free curved surface for lightdistribution may be formed on any one of the front surface and the backsurface of the lens 1.

[0081] In this invention, the NURBS, the free curved surface or thetorus curved surface corresponding to the free curved surface for lightdistribution may not be formed on the front surface and the back surfaceof the lens 1.

[0082] Although the invention has been described with respect to aspecific embodiment for a complete and clear disclosure, the appendedclaims are not to be thus limited but are to be construed as embodyingall modifications and alternative constructions that may occur to oneskilled in the art which fairly fall within the basic teaching hereinset forth.

What is claimed is:
 1. A lamp device for a vehicle comprising: a lightsource; a reflector in which a reflection surface is a free curvedsurface; a lens having no prism; and a reflected light by said reflectortransmitting through said lens so as to be irradiated to an externalsection in accordance with a target light distribution pattern, whereinsaid lens is formed in a convex shape in a vertical cross section and ahorizontal cross section.
 2. The lamp device for a vehicle according toclaim 1, wherein the reflection surface of said reflector is structuredsuch that the vertical cross section and the horizontal cross sectionare formed in a substantially hyperboloidal surface smaller than saidlens.
 3. The lamp device for a vehicle according to claim 1, wherein afree curved surface formed on the reflection surface of said reflectoris a non-uniform rational B-spline surface (NURBS).
 4. The lamp devicefor a vehicle according to claim 2, wherein a free curved surface formedon the reflection surface of said reflector is a non-uniform rationalB-spline surface (NURBS).
 5. The lamp device for a vehicle according toclaim 1, wherein a torus curved surface or a free curved surface isformed on a front surface or/and a back surface of said lens.
 6. Thelamp device for a vehicle according to claim 2, wherein a torus curvedsurface or a free curved surface is formed on a front surface or/and aback surface of said lens.
 7. The lamp device for a vehicle according toclaim 3, wherein a torus curved surface or a free curved surface isformed on a front surface or/and a back surface of said lens.
 8. Thelamp device for a vehicle according to claim 4, wherein a torus curvedsurface or a free curved surface is formed on a front surface or/and aback surface of said lens.